<p>不要使用<code>input</code>,因为它在等待输入时阻塞了线程(GUI使用的主线程)。相反,使用<code>Entry</code>作为<code>input</code>,而{<cd4>}作为{<cd5>},因为这是一个<em>GUI</em>:</p>
<pre><code># File: farmer_john_field
# Author: Elijah Cherry
# Course: CS-1010
# Original Problem: Draw specified image and calculate area of darkened region
from tkinter import *
from tkinter import ttk
import math
root = Tk()
win = Canvas(root, width = 500, height = 500)
win.grid()
def main():
def display_image():
# point a = 200,200
# point b = 300,200
# point c = 300,300
# point d = 200,300
# points move clockwise from top left (north west) quadrant
# rectangle to fill rear area
rectangle_back = win.create_rectangle (200,200, 300,300, fill="gray")
# circles will be placed by top left corner and bottom right corner
circle_a = win.create_oval (200-50, 200-50, 200+50, 200+50, fill="white")
# a xtl, a ytl a xbr a ybr
circle_b = win.create_oval (300-50, 200-50, 300+50, 200+50, fill="white")
# b xtl, b ytl b xbr b ybr
circle_c = win.create_oval (300-50, 300-50, 300+50, 300+50, fill="white")
# c xtl, c ytl c xbr c ybr
circle_d = win.create_oval (200-50, 300-50, 200+50, 300+50, fill="white")
# d xtl, d ytl d xbr d ybr
# rectangle outline
rectangle_outline = win.create_rectangle (200,200, 300,300, outline="gray")
# texts (labels for points a b c d)
text_a = win.create_text (200,200, anchor="se", text="A", fill="black")
text_b = win.create_text (300,200, anchor="sw", text="B", fill="black")
text_c = win.create_text (300,300, anchor="nw", text="C", fill="black")
text_d = win.create_text (200,300, anchor="ne", text="D", fill="black")
def display_the_query():
query_label = Label(root,
text="Enter length of one side of the square ABCD: ")
query_entry = Entry(root)
# to be able to track the entry text
# . notation to attach it as an attribute
query_entry.var = StringVar()
# to attaching the attribute as the displayed text
query_entry['textvariable'] = query_entry.var
result_label = Label(root)
# to actually track the input each time there's a difference
# which essentially allows dynamically calculating the result
query_entry.var.trace_add('write',
lambda *_, var=query_entry.var, lbl=result_label: calcn(var, lbl))
query_label.grid()
query_entry.grid()
result_label.grid()
def calcn(var, result_label):
user_input = var.get()
if user_input:
length = float(user_input)
radius = length / 2
dark_area_result = math.pi * radius**(2)
result_label['text'] = "Area of shaded region = {:0.2f}".format(
dark_area_result)
display_image()
display_the_query()
main()
mainloop()
</code></pre>